Mobility of rock avalanches triggered by underground nuclear explosions

Several large rockslides and rock avalanches ranging in volume from 10(5) m(3) up to 10(8) m(3) were triggered by underground nuclear explosions at the Novaya Zemlia test site. Rapid filming of rock avalanche formation allowed direct measuring of the velocities of debris spreading. Dynamics of two case studies derived from the real time observations and from the analysis of debris morphology and grain size composition is discussed in details. Factors determining runout of artificial rock avalanches such as variability of debris grain size composition and topography of the transition and deposition zones are examined. Relationships of rock avalanche runout and their volume are determined and compared with those of the natural events of different origin. Critical conditions of slope failure occurrence depending on intensity of seismic effects of the explosions and slope angles are examined as well.